1. Field of the invention
The present invention relates to a carriage drive unit for driving a carriage supporting a magnetic head, and more particularly to a drive belt attachment construction in such a carriage drive unit.
2. Description of the Prior Art
FIG. 1 of the accompanying drawings illustrates a conventional carriage drive unit composed of a substantially rectangular carriage 1 supporting a magnetic head 2 and slidably mounted on a straight guide shaft 3. A pulley 5 is disposed near the carriage 1 and fitted over a rotatable shaft 4 of a drive motor (not shown) with a drive belt 6 in the form of a thin metal web being looped around the pulley 5. The drive belt 6 has opposite ends fastened by screws 7, 8 to opposite ends of a side wall of the carriage 1, and a central portion fixed by a screw 9 to a peripheral wall of the pulley 5.
Rotative power from the drive motor is transmitted through the pulley 5 to the drive belt 6, which is progressively coiled around the pulley 5 to cause the carriage 1 to slide along the guide shaft 3 for moving the magnetic head 2 to a desired position.
With the prior carriage drive unit thus constructed, the drive belt 6 is fixed under a certain tension to the carriage 1 at the time of assembly in order to eliminate unwanted slippage of the drive belt 6 on the peripheral surface of the pulley 5 and to keep the rotational angle of the pulley 5 and the distance the magnetic head 2 is moved in a constant relationship.
However, it is tedious and time-consuming to fasten the ends of the drive belt 6 to the carriage 1 while tensioning drive belt 6. It is also difficult to assemble the drive belt in order that the drive belt 6 is under optimum tension. Accordingly, the prior art has experienced difficulty in providing a carriage drive unit having a high accuracy of moving a carriage.